How to deal with a magnetised mechanical watch?

　　Once a watch is magnetised, the magnetic force alters the oscillation frequency of the balance wheel, which can significantly impact the lifespan of the watch. So, what should be done if a mechanical watch becomes magnetised?

　　Anti-magnetic methods for mechanical watches

　　1) Anti-magnetic specifications for mechanical watches

　　Japanese mechanical watches: These usually come in 3 types, either with no anti-magnetic marking, standard anti-magnetic marking, or enhanced anti-magnetic marking.

　　No anti-magnetic marking: Can resist a magnetic field of 1600A/m (equivalent to 20 Gauss).

　　Standard anti-magnetic (symbolised by an inverted 'U' with a horizontal line underneath): Can resist a magnetic field of 4800A/m (equivalent to 60 Gauss).

　　Enhanced anti-magnetic (symbolised by an inverted 'U' with two horizontal lines underneath): Can resist a magnetic field of 16000A/m (equivalent to 200 Gauss).

　　When discussing anti-magnetic specifications, one must mention the Rolex Milgauss. This watch utilises a proprietary Parachrom blue hairspring made from a rare-earth nickel-cobalt alloy, combined with a fully sealed soft-iron anti-magnetic shield that has virtually no openings, elevating its anti-magnetic capability to the level of 100000A/m, making it a benchmark for anti-magnetic timepieces.

　　2) Decay of magnetic fields with distance

　　The strength of a magnetic field is inversely proportional to the 2 power of the distance; as the distance increases, the magnetic field strength decays sharply.

　　For ordinary anti-magnetic mechanical watches, keeping them 5cm or more away from the aforementioned magnetic objects is safe enough. Even for mechanical watches not marked as anti-magnetic, simply keeping them slightly further away (more than 10cm) will suffice. In daily life, with just a little attention, you can easily avoid the hazards of magnetic fields to mechanical watches, so there is no need to panic about magnetism.

　　3) Examples of common magnetic objects

　　Mobile phones, telephone receivers, computers, electric shavers, radios, magnetic clasps on handbags, refrigerator doors, induction cookers, magnetic bracelets, magnetic pillows, etc.

　　How to demagnetise a mechanical watch

　　Firstly, vintage watches require particular care regarding anti-magnetism, as do watches fitted with vintage movements. Their materials were not manufactured using modern processes, so their anti-magnetic performance is weaker.

　　Secondly, ultra-thin watches are easily magnetised. Because the space inside an ultra-thin movement is small, conventional anti-magnetic measures (such as blocking magnetic fields with a thick case) are difficult to implement.

　　Furthermore, mechanical watches encounter magnetic fields more frequently and with greater intensity in modern life. Leaving aside the impact on timekeeping accuracy, allowing a watch to remain in a strong magnetic environment for a long time also causes significant damage to the movement. Mid-to-high-end watches are overwhelmingly dominated by mechanical movements; if even running accuracy cannot be guaranteed, then any other functions become redundant.